The present invention relates to an apparatus for evaporative cooling of a liquiform product, comprising a vacuum vessel with an inlet for steam-charged product, an outlet for the product and an outlet for condensed steam, the apparatus also including a circulation cycle for coolant liquid.
Heat treatment of liquid food products, such as milk, is a common industrial process today. By heating the product, extended shelf life will be obtained as a result of the extermination of micro-organisms which exist in the product. In sterilisation of the food product, this is heated to a temperature exceeding 100xc2x0 C. In order to rapidly heat to such temperatures, steam is employed. The heating may take place either directly or indirectly. In indirect heating, heat exchangers of different types are employed. In the direct heating, the steam is added direct to the product.
There are two types of direct heating of a liquid product, injection and infusion. In injection, steam is injected into the product in a closed system. Infusion implies that the product is finely divided and caused to pass through a steam-filled space. In both cases, the supplied steam rapidly and efficiently heats up the product to the desired temperature, and the product is then kept at this temperature for a certain, predetermined interval of time. The added steam must thereafter be removed from the product in order to avoid diluting it. This normally takes place by evaporative cooling, so-called flash cooling, in a vacuum vessel. During the process, the steam is released and condensed at the same time as the product is cooled down to the temperature it had before the heat treatment.
The evaporative cooling normally takes place in that the steam-charged product is fed under pressure into a vacuum vessel. When the product enters into the vacuum vessel, the liquid boils, the steam is released and rises up in the vessel, while the product is accumulated in the lower region of the vessel. Thus cooled, the product may be drawn off from the lower region of the vessel. The steam which, together with uncondendsable gases, leaves the product is to be condensed in order to be able to be led off to an outlet. The condensation can either take place in that the steam and the gases are fed into an additional vacuum vessel where the steam is cooled by being sprinkled with cold water, or that the steam is condensed in some form of water-cooled plate condenser or tube condenser. The plate or tube condenser may be integral in the first vacuum vessel, or alternatively be placed outside it.
The various apparatuses existing today for condensing the steam are relatively expensive to manufacture, since in the first case an extra vacuum vessel is required or alternatively some form of condenser is needed. For the conventional method of condensing the steam, a considerable quantity of coolant water is moreover consumed, which should be of good quality in order to avoid xe2x80x9cfurringxe2x80x9d or scaling and corrosion on the plates or tubes in the condenser.
One object of the present invention is to realise an apparatus for the evaporative cooling (xe2x80x9cflash coolingxe2x80x9d) of a liquid, where the condensation of the released steam takes place in the same vacuum vessel and where no expensive and complicated condenser is required.
A further object of the present invention is that the coolant liquid which condenses the steam is circulated in a closed cycle, which reduces the consumption of coolant water and obviates the problem inherent in furring or scaling and corrosion.
These and other objects have been attained according to the present invention in that the apparatus of the type disclosed by way of introduction has been given the characterising features that the vessel is divided into a first and second space, concentrically disposed in the vessel and open towards the upper end of the vessel, and in which the inlet and outlet for the product are placed in the first space, and that the outlet for the condensed steam is placed in the second space.
Preferred embodiments of the present invention have further been given the characterising features as set forth in the appended subclaims.